SHAFAQNA –The United Steelworkers union said on Saturday the strike by U.S. refinery workers is expanding to two more plants early on Sunday due to unfair labor practices by oil companies.Walk-outs at BP Plc’s Whiting, Indiana, refinery and the company’s joint-venture refinery with Husky Energy in Toledo, Ohio, shortly after 12 a.m. local time on Sunday would bring the number of plants with striking hourly workers to 11, including nine refineries accounting for 13 percent of U.S. refining capacity.

BP said on Friday it had received notice of the walk-outs at the two refineries, but the Steelworkers had said little about them until Saturday.

The union said in a statement that U.S. refinery owners led by Royal Dutch Shell Plc have failed to discuss health and safety issues and engaged in “bad-faith bargaining, including the refusal to bargain over mandatory subjects; undue delays in providing information; impeded bargaining; and threats issued to workers if they joined the strike.”

A Shell spokesman said the company was unaware of any unfair labor practice charge filed against it with the U.S Department of Labor.

“We regret that we have been unable to reach a mutually satisfactory agreement with the USW prior to contract expiration,” said Shell spokesman Ray Fisher. “We remain committed to resolving the remaining issues through collective bargaining at the bargaining table.”

Saturday was the seventh day of the strike, which the USW called on Jan. 31 after it said Shell had walked away from the negotiating table.

About 4,000 workers at refineries in California, Kentucky, Texas and Washington initially left their jobs when the strike began shortly after midnight on Feb. 1.

Another 1,440 workers will join the picket lines when employees of the BP-operated refineries in Indiana and Ohio leave their jobs early on Sunday.

Oil companies are continuing to operate all but one of the plants with temporary replacement workers. BP said replacement workers would take over operations at the Whiting and Toledo refineries.

Tesoro Corp elected to shut down production at its Martinez, California, refinery by the end of this week because half the plant’s production was already shut due to a planned overhaul.

The USW began negotiations on Jan. 21 with Shell initially seeking wage increases, a tighter policy to prevent worker fatigue and reductions in non-union contractors working in refineries.

Since the start of the strike, the union has stressed the safety and health aspects of its proposals to prevent accidents in refineries.

“Management cannot continue to resist allowing workers a stronger voice on issues that could very well make the difference between life and death for too many of them,” said USW International President Leo Gerard, according to the statement issued on Saturday.